1. Field of the Invention
The present invention relates to a process for preparing an optically active alcohol and a process for preparing an optically active amine.
2. Description of the Related Art
As a process for preparing an optically active alcohol, for example, there is known a process comprising reacting an optically active .beta.-aminoalcohol and a borane in an amount of two moles per one mole of said aminoalcohol, and then reacting a prochiral ketone in an amount of 0.8 mole per one mole of said aminoalcohol with a reaction product (see, for example, J. Chem. Soc. PERKIN TRANS. I., 2039 (1985)).
However, this process has a drawback that a large amount of the expensive borane should be used.
To solve such drawback, JP-A-7-109231 discloses a process for preparing an optically active alcohol using a metal borohydride which is cheap and easily available in an industrial scale, that is, a process comprising reacting a mixture of a 2-substituted oxazaborolidine having substituents on a boron atom and a metal borohydride with an acid, and then reacting a prochiral ketone with a reaction product to obtain an optically active alcohol. But, the optical purity of the produced optically active alcohol is unsatisfactory, and further improvement of the process has been desired.
As a process for preparing an optically active amine, there is proposed a process comprising reacting an optically active .beta.-aminoalcohol with a borane, and then reacting a syn or anti-form of an oxime derivative with a reaction product, whereby an optically active amine having a desired absolute configuration is prepared (see JP-A-63-99041 and Tetrahedron Lett., 29223 (1988).
However, this process has a drawback that a large amount of an expensive borane should be used.
To solve such drawback, JP-A-2-311446 and JP-A-5-9158 disclose a process for preparing an optically active amine using a metal borohydride which is cheap and easily available in an industrial scale, that is, a process comprising reacting an optically active .beta.-aminoalcohol with a metal borohydride and an acid, and then reacting an oxime derivative with a reaction product.